Ultrasonic atomizer, ultrasonic inhaler and method of controlling same

ABSTRACT

A bush ( 31 ) is fitted into a housing ( 10 ) and an ultrasonic pump ( 12 ) is supported liquid tightly by the bush ( 31 ). The ultrasonic pump ( 12 ) is constituted by a pump shaft ( 21 ) formed to include a pump bore ( 22 ) passing through it axially and having upper and lower ends which are open, and an ultrasonic vibrator ( 23 ) mounted on the pump shaft ( 21 ) in the vicinity of the midpoint thereof in terms of the axial direction. A liquid vessel ( 16 ) is mounted in the housing ( 10 ) in a freely attachable and detachable manner, and the lower end portion of the pump shaft ( 21 ) is received inside the liquid vessel ( 16 ). A cap ( 15 ) is freely detachably attached to the upper end portion of the housing ( 10 ) so as to cover the upper end portion of the pump shaft ( 21 ). The top side of the cap ( 15 ) is provided with a spray port ( 51 ), and a step portion ( 57 ) is formed for supporting a mesh plate ( 14 ) at the periphery thereof at a position below the spray port ( 51 ). A compression spring ( 42 ) is provided between a portion of the top side of the cap and the mesh plate. The mesh plate ( 14 ) is formed to have a multiplicity of minute holes ( 14   a ) and is held in pressured contact with the upper end face of the pump shaft ( 21 ) by the compression spring ( 42 ).

TECHNICAL FIELD

This invention relates to an ultrasonic atomizer for pumping up a liquidfrom a liquid vessel by an ultrasonic pump and atomizing the liquid bypassing it through a mesh plate formed to have multiplicity of minuteholes, an ultrasonic inhaler serving as one application of theultrasonic atomizer, and a method of controlling the operation of theinhaler.

BACKGROUND ART

A known example of an ultrasonic atomizer of this type is described inthe specification of Japanese Utility Model Application Laid-Open No.3-15674. The atomizer described in this literature is characterized byuse of a mesh plate having tapered minute holes which flare from oneside of the plate toward the other. The mesh plate is arranged in such amanner that the side in which the minute holes have the openings oflarger diameter opposes the upper end face of the pump shaft of anultrasonic pump, and such that a minute gap is produced between the meshplate and the upper end face of the pump shaft.

In an ultrasonic atomizer, it is important to achieve balance betweenthe amount of liquid pumped by the ultrasonic pump and the amount ofatomization produced by the mesh plate. When there is a minute gapbetween the upper end face of the pump shaft and the mesh plate, as inthe document mentioned above, the amount of liquid pumped tends to belarger than the amount of liquid atomized. The liquid that is notatomized flows down from the gap to the upper portion (the horn) of thepump shaft and becomes a load on ultrasonic vibration at the horn. Thiscauses an unstable spraying operation and can lead to cessation ofoperation in some cases.

Another problem is that the user's fingers become soiled when liquidthat has not been atomized flows out of the device. An importanttechnical problem is assuring the liquid tightness of the device.

The number of minute holes formed in the mesh plate has a directinfluence upon the amount of atomization. The greater the number ofminute holes per unit surface area, the greater the amount ofatomization. When the number of minute holes is increased, however,there is a decline in the strength of the mesh plate itself. There is aneed for some expedient which can provide strength while allowing anincrease in the number of minute holes.

Since the mesh plate described in the above-mentioned document is suchthat the minute holes have aperture diameters that differ on the twosides of the plate, care must be taken in terms of the orientation ofthese sides when the mesh plate is mounted in the atomizer.

An ultrasonic atomizer can be applied to an ultrasonic inhaler, as setforth above. Medicines of higher cost than inexpensive water andphysiologic saline solutions are often used in inhalers. Accordingly,arranging it so that every drop of the medicine is used once the inhalerhas been filled is important in terms of economy.

Another requirement of an inhaler is that the user repeat the operationfor spraying the inhalant and halt this operation in conformity withbreathing. Control of the spraying operation is achieved by having theuser turn an operating switch on and off. However, turning the operatingswitch on and off often is troublesome or difficult particularly for theelderly or children. There is a need to arrange it so that the liquid issprayed automatically and intermittently in conformity with the user'sbreathing.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a structure in anultrasonic atomizer which makes it possible to achieve balance betweenamount of liquid pumped and amount of liquid atomized so that efficientand stable atomization can be obtained.

Another object of the present invention is to facilitate cleaning andreplacement of the mesh plate.

A further object of the present invention is to provide a mesh platehaving sufficient strength.

Yet another object of the present invention is to increase the amount ofatomization by increasing the number of minute holes in the mesh plate.

Another object of the present invention is to improve liquid tightnessof the device without limiting the vibration of a horn on the ultrasonicpump.

Another object of the present invention is to provide a structure whichwill not allow any excess liquid not atomized to flow out of the device.

A further object of the present invention is to enable effectiveutilization of liquid with which the device has been filled.

A further object of the present invention is to provide an inhaler, aswell as a method of controlling the inhaler, in which it is possible toachieve automatic, intermittent spraying that conforms to the breathingof the user.

An ultrasonic atomizer according to the present invention comprises anultrasonic pump comprising a pump shaft formed to have a pump borepassing through it axially and having open upper and lower ends, and anultrasonic vibrator mounted on the pump shaft in the vicinity of themidpoint with respect to the axial direction, a liquid vessel providedat a position at which it is penetrated by a lower end of the pumpshaft, a mesh plate placed on an upper end face of the pump shaft andformed to have a multiplicity of minute holes, and a biasing resilientmember for biasing the mesh plate toward the upper end face of the pumpshaft.

The pump shaft also is vibrated in the axial direction by vibration ofthe ultrasonic vibrator, whereby the liquid inside the liquid vessel ispumped up through the pump bore of the pump shaft. Since the mesh plateis urged against the upper end face of the pump by the resilient member,the mesh plate also vibrates by following up the motion of the pumpshaft. Owing to the fact that the mesh plate is vibrated, and by virtueof the fact that the mesh plate is biased by the resilient member, themesh plate acts as a type of valve which opens and closes the opening atthe upper end of the pump bore in the pump shaft. The liquid pumped whenthe valve is opened is supplied to the mesh plate. When the valve isclosed, the liquid is passed through the mesh plate so as to be atomizedand sprayed. Since liquid in the amount pumped is atomized, good balanceis achieved between the amount of liquid pumped and the amount of liquidatomized, and the spraying operation carried out is efficient andstable.

Since the mesh plate should be brought into pressured contact with theupper end face of the pump shaft at least in the vicinity of the openingat the upper end thereof, it is preferred that the following structurebe adopted:

In a preferred embodiment, the upper end face of the pump shaft isformed to have a shape in which the upper end face is slightly andsmoothly curved so as to attain maximum height at the position of theopening in the upper end of the pump bore and diminish in height as theperiphery is approached.

In case of an arrangement in which the mesh plate is biased by theresilient member at a peripheral edge extending outwardly from the upperend face of the pump shaft, the mesh plate curves slightly. Thecurvature of the upper end face of the pump shaft, the elastic force ofthe resilient member and the strength of the mesh plate are decided insuch a manner that the degree to which the mesh plate curves is lessthan the degree of curvature of the upper end face of the pump shaft.

In another embodiment, the upper end face of the pump shaft is formed tohave a protuberance which projects in an area that includes the openingin the upper end of the pump bore.

In another embodiment, the mesh plate is formed to have a shape in whichthe central portion thereof is bent or curved slightly so as to pointdownward.

In a further embodiment, the biasing resilient member is a compressioncoil spring having a coil diameter which becomes progressively smalleras the mesh plate is approached, in such a manner that the mesh plate isbiased at a position thereof situated on the upper end face of the pumpshaft.

As set forth in the above-mentioned document, it is preferred that themesh plate used be formed in such a manner that the minute holes flareoutwardly in the direction extending from the top side to the bottomside of the mesh plate.

An arrangement recommended to heighten the density of the minute holesin the mesh plate is one in which the minute holes are formed at equalintervals long the sides of a multiplicity of regular hexagons whosediagonals vary at fixed distances.

The present invention also provides other improvements relating to themesh plate. One is a mesh plate in which small areas devoid of theformation of minute holes are present in areas surrounded by minuteholes. Since the mesh plate has a multiplicity of minute holes, it isnearly impossible to inspect all of the them. Accordingly, if minuteholes to be inspected are specified using the small areas devoid ofminute holes as a reference, it becomes possible to inspect minute holesat the same positions at all times.

In another mesh plate, an area devoid of the formation of minute holesis present over a region broader than the opening in the upper end ofthe pump bore of the pump shaft at a location opposing the opening inthe upper end. By virtue of this arrangement, the above-described valveaction is attained more effectively.

In yet another mesh plate, cut-outs of different size are formed in theperiphery of the mesh plate at least at two locations other thanlocations having point symmetry about the center of the mesh plate.

The mesh plate is placed upon or attached to the step portion or someother location on a cap, described below. If a mesh-plate supportingmember provided on such as a cap is provided with projections that matewith the two cut-outs mentioned above, it will be possible to attach anddetach the mesh plate without mistaking the surface orientation of themesh plate. This is convenient for mesh plates having minute holes whoseopenings differ in size depending upon the particular side.

In another preferred embodiment of an ultrasonic atomizer according tothe present invention, there are further provided a housing, to whichthe liquid vessel is attached in a freely detachable manner, forsupporting the ultrasonic pump, and a cap attached to a portion of thehousing in a freely detachable manner so as to cover the upper end ofthe pump shaft. The top side of the cap is provided with a spray portand a step portion is formed for supporting the mesh plate at theperimeter thereof at a position beneath the spray port. The biasingresilient member is provided between a portion of the top side of thecap and the mesh plate.

When the cap is attached to the housing, the mesh plate is biased by theresilient member and brought into contact with the upper end face of thepump shaft. Thus, positioning of the mesh plate can be achieved withease. Since the mesh plate is provided on the cap, cleaning orreplacement (inclusive of replacement of the cap) is facilitated.

In yet another embodiment, the peripheral portion of the mesh plate isprovided with an annular plate, or a spacer is provided between the meshplate and the upper end face of the pump shaft, in order that thebiasing force produced by the biasing member may be applied to the meshplate uniformly.

The present invention provides a mesh plate having high strength. Themesh plate has two sides overall and is formed to have a multiplicity ofminute holes passing through it from one side to the other side. Eachminute hole flares outwardly from the one side to the other side, and asingle plate-shaped body is deformed continuously at the location ofeach minute hole in such a manner that a groove or recess is formedbetween mutually adjacent minute holes on the one side.

The present invention further provides an effective seal structure in anultrasonic atomizer. Specifically, in an ultrasonic atomizer comprisingan ultrasonic pump having a pump shaft formed to have a pump borepassing through it axially and having open upper and lower ends, and anultrasonic vibrator mounted on the pump shaft in the vicinity of themidpoint with respect to the axial direction, wherein a liquid inside aliquid vessel is pumped up from the lower end of the pump bore and theliquid is supplied to a mesh plate from the upper end of the pump boreso as to be sprayed, the present invention is characterized in thatthere is provided a bush for encircling and supporting liquid tightly aportion of the pump shaft of the ultrasonic pump excluding upper andlower end portions of the pump shaft, an annular seal lip, in intimateliquid-tight contact with a portion of the pump shaft situated higherthan the ultrasonic vibrator, formed integrally at least at twolocations, one above the other, on an upper portion of the bush, and agap provided between the portion of the pump shaft and the bush betweenthe annular seal lips at the at least two locations.

The liquid tightness of the ultrasonic pump within the bush is assuredby the annular seal lips. Further, the bush is not made to contact, overits entire surface, the upper portion (horn) of the pump shaft, whichundergoes large vibration; only the seal ribs are in partial intimatecontact with the upper portion of the pump shaft. As a result, vibrationof the horn is not attenuated.

The present invention further provides an ultrasonic atomizer having areservoir for collecting overflowing liquid not atomized. Specifically,the ultrasonic atomizer according to this aspect of the presentinvention comprises an ultrasonic pump having a pump shaft formed tohave a pump bore passing through it axially and having open upper andlower ends, and an ultrasonic vibrator mounted on the pump shaft in thevicinity of the midpoint with respect to the axial direction, a liquidvessel provided at a position at which it is penetrated by a lower endof the pump shaft, a mesh plate placed on an upper end face of the pumpshaft and formed to have a multiplicity of minute holes, a biasingresilient member for biasing the mesh plate toward the upper end face ofthe pump shaft, a bush for encircling and supporting liquid tightly aportion of the pump shaft of the ultrasonic pump excluding upper andlower end portions of the pump shaft, a housing in which the bush isfitted liquid tightly, and a cap attached in a freely detachable mannerto an annular projecting wall, which is formed on the housing about theupper end portion of the pump shaft, so as to cover the upper endportion of the pump shaft, a reservoir being formed with the top side ofthe bush serving as its bottom surface and at least one of the cap andannular projecting wall serving as its peripheral wall.

Liquid which has flowed into the reservoir is pumped along the pumpshaft by the vibration thereof and is eventually atomized. Accordingly,the liquid does not overflow to the exterior of the device and does soilthe fingers of the user. In addition, the liquid is used in an effectivemanner.

The present invention further provides an ultrasonic atomizer in whichliquid inside the liquid vessel can be utilized without any being leftunused.

The present invention is characterized in that, in an ultrasonicatomizer comprising a liquid vessel accommodating a liquid to beatomized, and an ultrasonic pump having a pump shaft formed to have apump bore passing through it axially and having open upper and lowerends, and an ultrasonic vibrator mounted on the pump shaft, a lower endof the pump shaft is disposed in close proximity to a bottom surface orside surface of the liquid vessel in such a manner that residual liquidremaining inside the liquid vessel is pumped upon attaching itself tothe lower end of the pump shaft by surface tension.

In a preferred embodiment, the liquid vessel is formed to have a recessfor collecting the residual liquid remaining inside the liquid vessel,and the lower end of the pump shaft is disposed so as to face therecess.

Even if the amount of liquid remaining in the liquid vessel is small,the liquid attaches itself to the lower end of the pump shaft and ispumped by virtue of surface tension and ultrasonic vibration so thatalmost all of the liquid is used for spraying purposes. This isparticularly effective when a costly medicine is used as the liquid.

Finally, the present invention provides an ultrasonic inhaler, and amethod of controlling the same, in which the inhaler has a learningfunction and spraying is rendered intermittent automatically at a periodthat substantially coincides with the period at which an operatingswitch is operated by the user.

Specifically, the present invention provides an ultrasonic inhalerhaving an ultrasonic pump comprising a pump shaft formed to have a pumpbore passing through it axially, and an ultrasonic vibrator mounted onthe pump shaft, wherein liquid is pumped through the pump shaft andsprayed by ultrasonic vibration, characterized by comprising a drivecircuit for driving the ultrasonic vibrator of the ultrasonic pump, anoperating switch, first control means responsive to on/off operation ofthe operating switch for controlling drive of the ultrasonic vibrator bythe drive circuit, and second control means which, in response to theoperating switch being turned on and off one time or a plurality oftimes, is for deciding ON time and OFF time (as by calculating averagevalue) in automatic intermittent operation on the basis of ON time andOFF time of the operating switch, and controlling the drive circuit insuch a manner that the ultrasonic vibrator is driven at a period of theON time and OFF time decided.

In an ultrasonic inhaler having an ultrasonic pump comprising a pumpshaft formed to have a pump bore passing through it axially, and anultrasonic vibrator mounted on the pump shaft, wherein liquid is pumpedthrough the pump shaft and sprayed by the ultrasonic vibrator, a methodof controlling the inhaler according to the present invention comprisesdriving the ultrasonic vibrator during time which an operating switch isON when the operating switch has been turned on, measuring the on time,halting drive of the ultrasonic vibrator during time which the operatingswitch is OFF when the operating switch has been turned off, measuringthe OFF time, deciding ON time and OFF time in automatic intermittentoperation on the basis of the measured ON time and OFF time of theoperating switch after the operating switch has been turned on and off aprescribed number of times, and driving the ultrasonic vibrator at aperiod of the on time and off time decided.

When the user turns the operating switch on and off a number of times inconformity with his or her own respiration, each of the on and off timesis measured to decide on and off times suited to the user. The devicethereafter enters an automatic intermittent-operation mode in which thespraying operation is performed intermittently at the period of the onand off times decided. This means that the user can breath withoutoperating the operating switch any further.

In an embodiment, the second control means is started so as to performthe automatic intermittent operation in response to on/off operation ofthe operating switch repeated a requisite plurality of times.Alternatively, the second control means makes a transition to theautomatic intermittent operation upon verifying that ON time of theoperating switch the last time in the requisite plurality of times isgreater than a first prescribed time.

In another embodiment, an automatic intermittent-operation mode switchis provided, the second control means is started so as perform theautomatic intermittent operation in response to an input from theautomatic intermittent-operation mode switch.

Preferably, third control means is provided for controlling the drivecircuit so as to drive the ultrasonic vibrator continuously in responseto ON time of the operating switch that is greater than a secondpredetermined time. As a result, spraying is performed continuously evenif the user no longer presses the operating switch.

It is further preferred that a manual mode in which the user operatesthe operating switch at all times be provided.

Other features and advantages of the present invention will be apparentin the description of an embodiment given with reference to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view, partially cut away, showing the overallconstruction of an ultrasonic atomizer;

FIG. 2 is an enlarged sectional view showing the principal mechanicalconstruction of the ultrasonic atomizer;

FIG. 3 is an enlarged plan view of a mesh plate;

FIG. 4 is an enlarged plan view showing another example of a mesh plate;

FIG. 5 is an enlarged plan view showing yet another example of a meshplate;

FIG. 6 is an enlarged sectional view showing a portion of a mesh plate;

FIG. 7 is an enlarged sectional view showing a portion of anotherexample of a mesh plate;

FIG. 8 is an enlarged sectional view showing a portion of a cap, a meshplate and a horn;

FIG. 9 is an enlarged sectional view showing another example of aportion of a cap, a mesh plate and a horn;

FIG. 10 is an enlarged sectional view showing yet another example of aportion of a cap, a mesh plate and a horn;

FIG. 11 is a perspective view showing another example of a mesh plate;

FIGS. 12a through 12 c show another example of a mesh plate, in whichFIG. 12a is a plan view, FIG. 12b a sectional view taken along line b—bin FIG. 12a and FIG. 12c a side view;

FIG. 13 is an enlarged sectional view showing another example of acompression spring;

FIG. 14 is an enlarged sectional view showing another example of abiasing resilient member;

FIG. 15 is an enlarged sectional view showing an example in which anannular plate is attached to a mesh plate;

FIG. 16 is an enlarged sectional view showing another example in whichan annular plate is attached to a mesh plate;

FIG. 17 is an enlarged sectional view showing an example in which aspacer is combined with a mesh plate;

FIG. 18 is an enlarged plan view of the spacer;

FIG. 19 is an enlarged plan view showing another example of a spacer;

FIG. 20 is a partially cut-away plan view of a liquid vessel;

FIG. 21 is a sectional view taken along line XXI—XXI of FIG. 20;

FIG. 22 is a circuit diagram showing an electric circuit of anultrasonic atomizer;

FIGS. 23 through 25 are flowcharts showing the processing procedure of aCPU; and

FIGS. 26a and 26 b are time charts showing the on/off operation of anoperating switch, the display on a display device and a transition toeach operating mode.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates the overall construction of an ultrasonic atomizer.In order to facilitate an understanding of the invention, the ultrasonicatomizer is shown somewhat larger than actual size.

The lower half portion of the ultrasonic atomizer extends vertically inthe form generally of a rectangle and has a cross section which isnearly a regular square, and the upper half portion is curved upward atan incline so as to point in the forward direction. The upper halfportion, especially the uppermost part of the device, is provided withthe principal mechanical components such as an ultrasonic pump 12, amesh plate 14 for atomizing the liquid pumped up by the pump, a cap 15holding the mesh plate 14, and a liquid vessel 16 accommodating a liquid(medicine or the like). These will be described later. The rear side ofthe upper half portion of the housing is covered by a freely detachablecover indicated by the chain lines. The cover is detached when theultrasonic atomizer is used.

Electric circuitry composed of a drive circuit of the ultrasonic pumpinclusive of an ultrasonic vibrator circuit, a control circuit havingvarious operating modes, and a power supply circuit is incorporatedwithin the lower half portion of the housing 10. These circuits will bedescribed later. A switch SW operated by the user and a display device(light-emitting diode) LED are provided on the back side of the upperhalf portion covered by the cover 11. The ultrasonic atomizer has aninternal chargeable battery. A jack 13 into which a plug led out from anexternal AC adapter or the like is plugged in order to charge thebattery is provided in a cavity in the lower portion of the housing 10.

FIG. 2 illustrates, in larger size, the principal mechanical componentsprovided in the upper half portion of the housing 10.

The ultrasonic pump 12 comprises a metallic pump shaft 21 having a small(diameter of not more than 1 mm) pump bore 22 passing through it in theaxial direction, and two piezoelectric elements (ultrasonic vibrators)23 secured to the pump shaft 21 substantially at its midpoint along thelength direction thereof. A flange 21 a is formed as an integral part ofthe pump shaft 21 at a portion of the pump shaft 21 somewhat above itsmidpoint. The piezoelectric elements 23 are annular in shape and arefitted over the pump shaft 21. Annular electrode plates 24 are providedon both sides of the piezoelectric elements 23. A nut 26 is screwed ontomale threads formed on the pump shaft 21 so that the piezoelectricelements 23 and electrode plates 24 are firmly secured to the pump shaft21 between the flange 21 a and nut 26. A high-frequency(ultra-high-frequency) voltage from the above-described drive circuit isapplied to the electrodes 24 through lead wires 25 so that thepiezoelectric elements 23 may vibrate ultrasonically mainly in the axialdirection of the pump shaft 21.

A pump bore 22 opens in the lower end face of the pump shaft 21 as wellas in the upper end face of the pump shaft 21. A lower end portion 21Bof the pump shaft 21 projects into the liquid vessel 16 and is submergedwithin the liquid inside the vessel 16. The pump shaft 21 has an upperend portion 21A serving as a horn, with the diameter of the upper endbeing made somewhat larger. The ultrasonic vibration of thepiezoelectric elements 23 is transmitted to the pump shaft 21 so thatthe pump shaft 21 also undergoes ultrasonic vibration in the axialdirection, as a result of which the liquid inside the liquid vessel 16rises within the pump bore 22 of the pump shaft 21. It is believed thatthis is ascribable to the force applied by the ultrasonic vibration, thesurface tension of the liquid and the negative pressure generated insidethe pump bore 22.

The above-described ultrasonic pump 12 is encircled by a waterproof bush31 comprising a resilient body (rubber, for example) and is secured tothe upper half portion of the housing 10 via the bush 31.

The bush 31 is constituted by an upper half body 32 and a lower halfbody 33. A space which accommodates the ultrasonic pump 12 is formedinside the upper half body 32 and lower half body 33. An annular groove32 ais formed in the bottom side of the upper half body 32 and anannular projection 33 a is formed in the top side of the lower half body33. The two bodies 32, 33 are joined to construct the bush 31 by matingthe projection 33 a with the groove 32 a. The upper portion of the lowerhalf body 33 is further formed to have an outwardly extending flange 33b. The upper half body 32 is tightly fitted into an accommodating recess10A formed in the housing 10. The lower half body 33 is supported insidea recess of a retaining member 38. The latter is secured to the housing10 at three locations (only one of which is shown) by means of screws39. Thus, the entire portion of the pump shaft 21, with the exception ofan upper end portion 21A and lower end portion 21B thereof, of theultrasonic pump 12 is covered water tightly by the bush 31, and the pumpshaft is secured to the housing 10.

Upper and lower portions of an inner circumferential surface of acylindrical portion formed on the upper half body 32 of the bush andpenetrated by the pump shaft 21 are formed to have inwardly projectingannular seal lips 34A, 34B as integral parts of the upper half body 32of the bush. The annular seal lips 34A, 34B are in intimate contact withthe outer circumferential surface of the pump shaft 21 and maintainliquid tightness. Between the seal lip 34A of the upper portion and theseal lip 34B of the lower portion, a small gap 35 is formed between theinner circumferential surface of the cylindrical portion of the upperhalf body 32 of the bush and the outer circumferential surface of thepump shaft 21. Since the area of contact between the upper half body 32of the bush and the upper portion (horn) 21A of the pump shaft 21 issmall, ultrasonic vibration of a large amplitude can be obtained at theupper portion of the pump shaft 21. The middle (flange 21 a, vibrators23, nut 26, etc.) of the ultrasonic pump 12 where the amplitude ofvibration is small is held tightly by the bush 31.

Similarly, with regard to the lower half body 33 of the bush, upper andlower portions of the inner circumferential surface of a cylindricalportion of the lower half body penetrated by the pump shaft 21 areformed to have inwardly projecting annular seal lips 36B, 36A asintegral parts of the lower half body 33. The seal lips 36A, 36B are inintimate contact with the outer circumferential surface of the lowerportion of pump shaft 21, whereby liquid tightness is maintained.Further, between the upper and lower seal lips 36B, 36A, a small gap 37is formed between the lower half body 33 and the pump shaft 21 to assurelarge ultrasonic vibration.

The periphery of the housing at a position where the upper end portion21A of the pump shaft 21 protrudes is integrally formed to have acylindrical portion (annular projection) 59, which is low in height, forthe purpose of attaching the cap 15. The outer circumferential portionof the cylindrical portion 59 is formed to have projections 59 a at twolocations.

The cap 15 is formed to have a spray port 51 in its top side. The bottomside of the cap is open. A base 52 is fitted into the cap 15. The base52 is formed to have a hole 53 through which the upper end portion ofthe pump shaft 21 is loosely passed, and the outer side of the base isformed to have an annular groove which receives the cylindrical portion59. The inner circumferential surface of the cap 15, which is formed bythe base 52 and cap 15, is formed to have vertical grooves (not shown inFIG. 2) through which the projections 59 a are passed, as well as agroove 55 leading to the upper ends of the vertical grooves and inclineddiagonally upward at a slight angle.

Accordingly, the cap 15 is secured to the cylindrical portion 59 (thisis the state shown in FIG. 2) by placing the cap on the cylindricalportion 59 at a position where the projections 59 a coincide with thevertical grooves and then turning the cap 15 slightly, whereby theprojections 59 a are fitted into the groove 55 and moved into the groove55. Thus, the cap 15 is capable of being attached to the housing 10 in afreely detachable manner. It goes without saying that the arrangementfor attaching the cap 15 to the cylindrical portion 59 a is not limitedto that described above. The cap can be attached by screws or simply bymating projections with recesses.

The upper portion of the base 52 of cap 15 is further formed to includean annular step 57 at a position facing a recess 54. The mesh plate 14,which is provided with a multiplicity of minute holes, is placed uponthe annular step 57. A compression spring 42 is provided between theperiphery of the mesh plate 14 and the periphery of the spray port 51 ofthe cap 15. In a state in which the cap 15 has been detached from thehousing 10, the mesh plate 14 is pressed against step 57 at theperiphery of the mesh plate by the compression spring 42. When the cap15 is attached to the cylindrical portion 59 of the housing 10, theupper end face of the pump shaft 21 abuts against the central portion ofthe mesh plate 14 and the periphery of the mesh plate 14 lifts upslightly from the step 57. The mesh plate 14 is biased in the directionof the upper end face of the pump shaft 21 at all times by the spring 42so that the mesh plate 14 will vibrate by following up the verticalvibration of the horn 21A. Liquid which has risen through the pump bore22 of the pump shaft 21 is atomized very finely through the mesh plate14 and is sprayed to the outside from the spray port 51. The details ofthe mesh plate 14 as well as the relationship among the mesh plate 14,the spring 42 and the upper end face of the pump shaft 21 will bedescribed in detail later.

The mesh plate 14 is attached to the cap 15. Since the cap 15 is freelyattachable and detachable with respect to the housing 10, it is easy toclean or replace the mesh plate 14 where replacement can meanreplacement of the mesh and cap). Further, positional adjustment of themesh plate 14 relative to the upper end face of the pump shaft 21 ismade unnecessary.

A space delimited by the top side of the upper half body 32 of the bushinclusive of the annular seal lip 34A, the outer circumferential surfaceof the horn 21A, the hole 53 in the base 52 and the recess 54 serves asa liquid overflow reservoir 56. In a case where the amount of liquidpumped to the upper end face of the horn 21A by the ultrasonic pump 12is greater than the amount of liquid atomized, as a result of which theliquid overflows from the upper end face of the horn 21A, and in a casewhere the user accidentally allows liquid to drip liquid, any liquidwill collect temporarily in the liquid overflow reservoir 56. Owing tothe ultrasonic vibration of the horn 21A, however, the liquid is pumpedup to the bottom side of the mesh plate 14 and atomized. Because theoverflow liquid is subsequently atomized in this manner, the overflowliquid does not remain around the horn 21A for an extended period oftime. If the overflow liquid was allowed to remain around the hornindefinitely, it would accumulate to the point that it attenuate thevibrational amplitude of the horn 21A. A decline in atomizationperformance or instability thereof ascribed to attenuation of thevibrational amplitude of the horn 21A or to some other cause can thus beprevented by ensuring that any overflow liquid does not accumulatearound the horn but rather is atomized in the manner described above.Further, since liquid which has overflowed from the upper end face ofthe horn 21A is prevented from flowing out to the exterior of thehousing 10, there is no risk of the user's fingers being soiled and lossof costly medicine can be prevented.

The retaining member 38 projects downwardly in the form of a cylinderfrom the portion surrounding the lower half body 33 of the bush and theperiphery of this cylindrical projection is provided with an O-ring 63.Further, an annular projection 38A is formed on the bottom side of theretaining member 38 on the outer side of the cylindrical projection. Theannular projection 38A preferably is partially broken off at a pluralityof locations. The liquid vessel 16, meanwhile, is formed from atransparent material. The top side of the vessel has an opening 61 theperiphery of which projects slightly in the form of a cylinder (theperiphery of the cylindrical opening is indicated at numeral 61A). Byinserting the cylindrical periphery 61A of the liquid vessel 16 betweenthe O-ring 63 and the annular projection 38A, the vessel 16 is fixedlyattached to the bottom side of the retaining member 38. The liquidvessel may thus be freely attached to and detached from the housing 10.Since the vessel 16 is transparent, the amount of liquid inside can beconfirmed visually from the outside. The top side of the vessel 16 isprovided with a small hole 62 communicating with the atmosphere. This isto prevent negative pressure from being produced inside the liquidvessel as a result of the liquid in the liquid vessel 16 being pumped bythe ultrasonic pump 12. The details of the structure of the vessel 16and the advantages thereof will be described later.

FIG. 3 is an enlarged plan view of the mesh plate 14. The mesh plate 14is provided with a multiplicity of minute holes 14 a, as mentionedabove.

The multiplicity of holes 14 a preferably are formed at equal intervalsalong the sides of a number of regular hexagons drawn with their centerson the center of the circular mesh plate 14, as well as at the apices ofthe hexagons. The lengths of the diagonals of the number of regularhexagons vary at fixed lengths from one hexagon to the next. The numberof minute holes 14 aalong one side of a regular hexagon differs from thenumber along one side of the adjacent hexagon by one. If thisarrangement is adopted, the number of minute holes 14 a per unit area ismaximized and the amount of liquid atomized is increased as a result.

FIG. 4 illustrates another example of the mesh plate 14. This mesh platehas two characterized features in addition to those mentioned above.

One feature is that blank portions 43 devoid of the minute holes 14 aare provided. There are a total of three blank portions 43 in FIG. 4,namely at a point at the center and at two points established atintervals of five minute holes from the center along one portion of adiagonal of the regular hexagons.

The mesh plate is formed to have a multiplicity of minute holes. In theprocess for manufacturing the mesh plate, at the time of delivery and atother necessary times, inspection is required in order to determinewhether the minute holes have been formed to the stipulated size andshape. Since it is virtually impossible to measure the diameters of allof the minute holes in this inspection, only specific minute holes areinspected. Since a change in the positions of minute holes to beinspected from one inspection to the next is undesirable, it is requiredthat minute holes located at specific positions at all times beexamined. If the blank portions 43 are provided as set forth above,minute holes that are to be examined can be determined using the blankportions 43 as a reference. For example, minute holes adjacent to andlocated on the outer side of the blank portions 43 may be examined. Inthis way the minute holes to undergo examination can be specified.

The other feature is that at least two types of cut-outs 44A, 44B ofdifferent size are formed at two respective locations (positions havingpoint symmetry about the center of the mesh plate are excluded) on theperiphery of the mesh plate 14. As will be described later, the meshplate 14 has a front surface and a back surface (or a top surface and abottom surface), and the mesh plate 14 must be installed in the cap 15in such a manner that one surface of the mesh plate comes into surfacecontact with the upper end face of the horn 21A. Projections 57A, 57B ofdifferent size are provided on the step portion 57 of the base 52 of cap15 and mate perfectly with the cut-outs 44A, 44B, respectively, of themesh plate 14 when the mesh plate 14 has been placed in the correctsurface orientation. If the cut-outs 44A, 44B are situated so as to matewith the projections 57A, 57B, the mesh plate 14 will be installed inthe cap 15 with its surfaces pointing in the correct directions.

A mesh plate 14 illustrated in FIG. 5 has still another characterizingfeature. This is the fact that a comparatively large closed portion 45is provided at the center of the mesh plate 14. No minute holes areformed in the closed portion 45. When the cap 15 having the mesh plate14 installed therein has been fitted on the housing 10, the closedportion 45 opposes the opening in the pump bore 22, which is open at theupper end face of the horn 21A, and acts to periodically close theopening as the opening vibrates. As a result, the valve action(described below) of the mesh plate 14 is reinforced so that moreefficient pumping and spraying can be expected. The closed portion 45should be large enough to close the opening in the upper end of the horn21A. However, since the substantial area over which the minute holes maybe provided is decreased if the closed portion is made too large, theclosed portion should be sized so as not to have a deleterious effectupon the atomizing action. It goes without saying that in a case wherethe opening in the upper end of the horn 21A is not at the center but isoffset to one side, the closed portion 45 also is provided in the meshplate 14 at a position offset from the center thereof so that it willoppose the opening in the upper end of the horn.

FIG. 6 illustrates a portion of the cross section of the mesh plate inenlarged form.

The diameter of the circular minute holes 14 a is small at the topsurface of the mesh plate 14. The holes become successively wider andthe diameter successively larger toward the bottom surface of the meshplate. A recess or groove 14 b opening toward the top surface is formedon the periphery of each minute hole 14 a, namely between the minuteholes 14 a. As a result, a shape is obtained in which the rim definingeach minute hole 14 a projects in the upward direction. The mesh plate14 is installed in the cap 15 in such a manner that the bottom surfaceof the mesh plate 14 opposes the upper end face of the horn 21A whilethe top surface opposes the spraying port 51 of the cap 15. This meshplate 14 is characterized in that a comparatively large strength isobtained without making the plate thick.

As for an example of the dimensions of the various portions constitutingthe mesh plate having the sectional configuration shown in FIG. 6, thepitch a of the minute holes 14 a is 50˜150 μm (a pitch on the order of100 μm is suitable), the diameter L of the opening of each minute hole14 a in the top surface is on the order of 4.5±1 μm, the thickness c ofthe mesh plate 14 is on the order of 30˜100 μm (a thickness on the orderof 50 μm is suitable). Such a mesh plate can be fabricated by combiningphotoetching and electroforming techniques. Specifically, a number ofelectrodes are formed on an insulative plate by photoetching so as tocorrespond to the positions of the centers of the recesses 14 b. Thisplate is adopted as a first negative. Next, a first metal is depositedon the electrodes by electroforming in such a manner that mutuallyindependent mountains are formed. The resulting plate is adopted as asecond negative. A second metal is further built up uniformly on eachmountain of the second negative by electroforming. If the secondnegative is then peeled off the deposited second metal, a mesh platecomprising the layer of the second metal will be obtained. If it isacceptable for the minute holes to be comparatively large, the meshplate having the shape shown in FIG. 6 can be fabricated by press workor injection molding.

FIG. 7 shows another example of a mesh plate, in which the cross sectionis illustrated in enlarged form. Each of the multiplicity of minuteholes 14 a flares downwardly in such a manner that the diameter of thecircular minute holes 14 a is small at the top surface of the mesh plate13 and becomes successively larger toward the bottom surface. Such ashape of the minute hole itself is known in the art. The material may bemetal or a plastic film. The minute holes need not be circular.

The directions in which the surfaces point when the mesh plate has beenmounted in the cap is important because the diameters of the minuteholes at the top surface and bottom surface differ.

FIG. 8 illustrates, in enlarged form, the shape of the upper end face ofthe horn 21A and the relationship among the mesh plate 14, thecompression spring 42 and the cap 15.

The upper end face of the horn 21A is formed so as to be slightly andsmoothly curved (spherically) in such a manner that the end faceprotrudes upwardly to the maximum extent at the center where the pumpbore 22 opens. The mesh plate 14 is held fast at its periphery by thecompression spring 42, as a result of which the mesh plate is caused toflex slightly. By way of example, the difference d between the highestand lowest points of the upper end face of the horn 21A is on the orderof 20˜50 μm, the amount of flexure of the mesh plate 14 is on the orderof 5˜10 μm, and the degree of curvature of the upper end face of thehorn 21A is greater than the degree of curvature of the mesh plate 14caused by flexing. It is important that the vicinity of the opening tothe pump bore 22 in the upper end face of the horn be pressed by themesh plate under the force of the compression spring 42. The degree ofcurvature of the upper end face of the horn, the strength of the meshplate and the spring force of the compression spring are selected so asto produce this relationship.

The vertical (up-and-down) vibration of the horn 12A is accompanied byup-and-down vibration of the mesh plate 14, as mentioned above. Thoughthe minute holes 14 a are formed in the mesh plate 14, overall the meshplate 14 acts as a valve which, by vibrating, opens and closes theopening in the upper end of the pump bore 22. Owing to this valve actionof the mesh plate 14, liquid pumped up from the pump bore spreads overthe upper end face of the horn 21A to form a liquid film when the valveis opened. When the valve is closed, the pumping action is suppressedand the above-mentioned liquid film is atomized through the mesh plate14. In other words, pumping and atomization are performed alternately sothat the amount of liquid pumped and the amount of liquid atomizedbalance each other, whereby an efficient, stabilized spraying action isachieved. According to tests and experiments carried out by theinventors, a spraying operation exhibiting stable performance wasachieved. At present the reasons are believed to be as set forth above.With a mesh plate having the closed portion 45, as shown in FIG. 5, theabove-described valve operation can be expected to be attained with evengreater efficiency. The pumping effect produced by the valve action ofthe mesh plate is particularly important at the beginning of thespraying operation.

FIG. 9 illustrates another embodiment. Here the upper end face of thehorn 21A is flat and the mesh plate 14 is curved so as to projectdownward. FIG. 11 is a perspective view of the mesh plate 14. Anotherexample of a mesh plate usable in the arrangement shown in FIG. 9 isillustrated in FIGS. 12a through 12 c. Here the mesh plate 14 is foldedslightly and smoothly along a boundary which is a straight line passingthrough the center of the mesh plate. The minute holes are deleted fromthe illustrations in FIG. 11 and in FIGS. 12a through 12 c.

FIG. 10 illustrates yet another embodiment. Here the portion of theupper end face of horn 21A surrounding the opening in the upper end ofthe pump bore 22 protrudes slightly (the protruding portion is indicatedat 21C).

In all of the examples described above, the diameter of the coilcompression spring is set to be the same at all portions. Thearrangement is such that the compression spring urges the periphery ofthe mesh plate extending outwardly of the upper end face of the horn. Asa consequence, the mesh plate is caused to curve into an upwardlydirected projection, and hence there is the possibility that the meshplate will not be able to close off the opening in the upper end of thepump bore. In order to arrange it so that the opening in the upper endof the pump bore can be constrained by the mesh plate, the upper endface of the horn is curved so as to project upward, a projection isformed or the mesh plate is curved into a downwardly directlyprojection.

By contrast, when a compression spring according to a modification shownin FIG. 13 is used, it is unnecessary to work the upper end face of thehorn or the mesh plate. Here the upper end face of the horn is flat andthe mesh plate 14 is flat as well. The compression spring 42 has a smalldiameter at its lower portion, with the diameter of the spring growinglarger from the bottom to the top. The compression spring 42 urges themesh plate 14 at the portion thereof on the upper end face of the horn21A.

FIG. 14 illustrates another example of the biasing resilient member.Here an annular sponge 46 is used instead of the spring.

With the compression spring described above, the biasing force appliedto the mesh plate will not necessarily be uniform. Accordingly, as shownin FIG. 15, it is recommended that an annular plate 47 simply be placedon the periphery of the mesh plate 14 or that the annular plate be fixedto periphery of the mesh plate 14 by bonding or welding, with theannular plate 47 being urged from above by the compression spring.

FIG. 16 shows an example in which the width of the annular plate 47 isenlarged so that the inner circumferential portion thereof engages theupper end face of the horn. In this case the upper end face of the horn21A may be flat.

FIG. 17 illustrates an example in which a spacer 48 instead of theannular plate 47 is interposed between the mesh plate 14 and the upperend face of the horn. As shown in FIG. 18 or 19, the spacer 48 isintegrally formed to include a small circular portion at its center, anannular portion along its circumference and radiating connecting spokesconnecting these two portions. The small circular portion at the centershould be sized so as to cover the opening of the pump bore 22 in theupper end face of the horn. The upper end face of the horn 21A may beflat. The annular plate 47 and spacer 48 may both be made of metal orplastic.

The shape of the liquid vessel 16 will now be described with referenceto FIGS. 2, 20 and 21.

The liquid vessel 16 has a rear wall 65 sloping downward toward thefront. Further, both side portions 64A, 64B at the rear of a bottom wall64 also slope upwardly toward the sides of the vessel. Since theprincipal mechanical portions of the ultrasonic atomizer are provided inan attitude in which they are inclined downwardly and forwardly, asshown in FIG. 1, the front portion of the bottom wall 64 is inclineddownwardly and rearwardly in the state where the liquid vessel 16 isattached. In this way the liquid vessel 16 is formed to have its deepestrecess 66, which is delimited by four inclined surfaces 64, 64A, 64B and65. The lower end portion 21B of the pump shaft 21 is situated directlyabove the recess 66 in close proximity thereto and in fairly closeproximity to the rear wall 65. By way of example, the distance betweenthe lower end face of the pump shaft 21 and the bottom of the recess 66is on the order of 2˜3 mm, and the distance between the rear wall 65 andthe part of the peripheral surface of the lower end of the pump shaft 21that is nearest to the rear wall 65 is on the order of 1 mm.

In use of the ultrasonic atomizer, the liquid vessel 16 is filled withan appropriate amount of liquid, i.e., to such an extent that the liquidwill not overflow. The liquid in the liquid vessel 16 decreases as thedevice is operated to spray the liquid. When the amount of liquidbecomes small, the liquid collects in the deepest recess 66. When thisoccurs, a small amount of the liquid attaches itself to the lower end ofthe pump shaft 21, as shown at W in FIG. 2, and the liquid is pumped andsprayed to the last drop, owing to the energy of ultrasonic vibration(negative pressure) and the surface tension of the liquid. Thus, all ofthe liquid introduced to the interior of the liquid vessel 16 is used upwithout even a single drop being wasted. If the liquid is inexpensive,as in the case of water or a physiological saline solution, there is noparticular inconvenience if some is left. If the liquid is a costlymedicine, however, using up all of the liquid in the manner describedabove is economical since waste is avoided.

Finally, the electrical construction of the ultrasonic atomizer will bedescribed with reference to FIG. 22.

The electrical circuitry incorporated within the housing 10 of theultrasonic atomizer comprises a CPU (microprocessor) 70 which controlsoverall operation, a DC/DC converter 71, an oscillator circuit (anddrive circuit) 72, a gate circuit 73, a switch-status detecting circuit74, a power-supply circuit 75, a display circuit 76 and a battery 79.

The operating voltage of the battery 79 is converted by the DC/DCconverter 71 to a voltage suited to the operation of the oscillatorcircuit 72, and the converted voltage is applied to the oscillatorcircuit 72, which generates a high-frequency (ultrasonic) signal.

As will be described later, the oscillating operation of the oscillatorcircuit 72 is controlled by the CPU 70 via the gate circuit 73. The gatecircuit 73 comprises a resistor R₁ and a MOS transistor Q₁. The startingand stopping of the oscillating operation of the oscillator circuit 72is controlled in conformity with the voltage level (H level or L level)which the CPU 70 outputs from an output terminal O₁. When the oscillatorcircuit 72 operates, the output high-frequency signal is applied to thepiezoelectric element 23 through a lead wire 25, whereby the ultrasonicpump 12 operates to perform atomization in the manner set forth above.

The switch-status detecting circuit 74 detects the on/off state of theswitch SW operated by the user and applies the result of detection tothe CPU 70. The operating switch SW is one type of push-button switch.The switch SW is ON during the time it is being pressed by the user andis turned off when the hand of the user is removed from the operatingswitch SW. The detecting circuit 74 comprises the operating switch SW, adiode D₁ and a pull-up resistor R₂. When the operating switch SW isturned on, an L-level voltage enters the CPU 70 from its input terminalI₁. If the switch is off, a high-level voltage enters the CPU 70 fromits input terminal I₁.

The power-supply circuit 75 controls the supply of operating power fromthe battery 79 to the CPU 70. The power-supply circuit 75 comprisestransistors Q2, Q3 and resistors R3, R4, R5, R6 and R7.

When the operating switch SW is turned on, the transistor Q3 turns on,as a result of which power is supplied to the CPU 70 through thetransistor Q3. Operating power is supplied to the CPU 70 irrespective ofthe status of transistor Q2 as long as the switch SW is kept in the ONstate.

Once operating power is supplied to the CPU 70, the CPU 70 continues todeliver an H-level ON signal to its output terminal O₂ except in a casewhere the supply of power is cut off under fixed conditions, as will beunderstood from a description given later. The transistor Q₂ is turnedon by this H-level ON signal. Even if the operating switch SW is turnedoff, the transistor Q₃ is held in the ON state so that the CPU 70continues to be supplied with operating power. When the CPU 70 judgesthat the power supply should be turned off, it inverts the output signalat the output terminal O₂ to the L level. When this is done, thetransistor Q2 turns off and the transistor Q3 turns off as long as theswitch SW is off. The supply of power to the CPU 70 is halted as aresult. Thereafter, power is not supplied to the CPU 70 as long as theuser does not turn on the switch SW.

The display circuit 76, which controls the lighting or flashing of adisplay device LED, includes a resistor R₈. The CPU 70 causes the Llevel to appear at an output terminal O₃ thereof in a case where thedisplay device LED is lit. If the display device LED is to be flashed,the CPU outputs a pulse signal of a fixed period (e.g., 5 Hz) at itsoutput terminal O₃. If the output terminal O₃ is at the H level, thedisplay device LED remains extinguished. It goes without saying thatlighting or flashing of the display device LED is performed only in acase where the transistor Q₃ is ON, thereby applying the operatingvoltage to the CPU 70 and display device LED.

According to this embodiment, there is a continuous-operation mode andan automatic intermittent-operation mode.

In the continuous-operation mode, the spraying operation proceeds incontinuous fashion even if the operating switch SW is OFF. As shown inFIG. 26a, a transition is made to the continuous-operation mode when theoperating switch SW is pressed continuously for more than four seconds.The transition is made to the continuous-operation mode also in a casewhere the operating switch SW is pressed continuously for more than fourseconds when the automatic intermittent-operation mode (described next)is in effect and in the course of making a transition to the automaticintermittent-operation mode.

In the automatic intermittent-operation mode, the spraying operation andthe halting thereof are repeated at a fixed period even if the operatingswitch SW is OFF. This period of intermittent spraying is decided bylearning. As shown in FIG. 26b, a transition is made to the automaticintermittent-operation mode by having the user turn on the operatingswitch repeatedly three times, wherein the switch is turned on for lessthan four seconds each of the three times. In the course of thistransition, the CPU 70 learns the period at which the operating switchis turned on and off (namely the ON time and the OFF time) and decidesthe period of intermittency (the ON/OFF repetition period) in theautomatic into intermittent-operation mode.

The automatic intermittent-operation mode is particularly effective in acase where the ultrasonic atomizer is applied to an inhaler. In aninhaler, atomized medicine is drawn in to the throat only when the userinhales. The medicinal inhalant used is expensive. In order to preventwasteful use of the medicine, it is necessary to repeat the sprayingoperation and the termination thereof in conformity with the user'sbreathing. In the learning process, the period (time) at which the userturns the operating switch on and off is measured, whereby learning isperformed. Even if the switch SW is not turned on and off afterlearning, the spraying operation and termination thereof are repeatedautomatically at a repetition period that conforms to the user'sbreathing. This is particularly useful for the elderly and children, whocannot perform the on/off operation skillfully.

If the operating switch SW is pressed again in the continuous-operationmode and automatic intermittent-operation mode and this ON time is lessthan four seconds, supply of power to the CPU 70 is halted (transistorQ₂ is turned off). Further, the power supply is turned off also in acase in which the switch SW is turned off for more than five seconds inthe course of the transition to the automatic intermittent-operationmode (i.e., in the course of the learning process).

The flowcharts shown in FIGS. 23 through 25 illustrate theabove-described operation in accordance with the processing procedure ofthe CPU 70.

The operation of the CPU 70 is started in response to the operatingswitch SW being turned on by the user. When the operating switch isturned on, the CPU 70 outputs an H-level signal at its output terminalO₂, thereby turning on the transistor Q₂ (step 111). As a result, theoperating voltage is applied to the CPU 70 irrespective of the on/offoperation of the switch SW, as described above.

If the operating switch SW is turned on continuously for more than fourseconds (YES at step 112), a transition is made to thecontinuous-operation mode and a display to this effect is presented(step 113). After the operating switch SW has been kept in the ON statecontinuously for four seconds, the display device LED starts to flashand continues flashing until the switch is turned off, therebyindicating the fact that a transition has been made to thecontinuous-operation mode, as shown in FIG. 26a. The display device LEDremains lit until elapse of four seconds from the moment the operatingswitch SW is turned on as well as during operation in thecontinuous-operation mode. The spraying operation is performedcontinuously from the moment the operating switch SW is turned on.

The spraying operation in the continuous-operation mode continues aslong as the operating switch SW is not turned off subsequently (NO atstep 114) and the operating switch SW is not turned on again (NO at step115).

If the operating switch SW is turned on (YES at step 115) and this ONtime is less than four seconds (NO at step 116 and YES at step 117),then the CPU 70 sends the output at its output terminal O₂ to the Llevel to cut off the supply of electric power (step 118).

In a case where the ON time of the operating switch SW is greater thanfour seconds (YES at step 116), then processing for a transition to thecontinuous-operation mode is performed again (step 113).

In a case where the operating switch SW is turned on and the ON time isless than four seconds (NO at step 112 and YES at step 119), a learningcounter N is cleared (step 120).

When the operating switch SW is turned on again (YES at step 122), theresults of the first learning operation, namely the results of measuringthe preceding ON and OFF times of the switch, are accepted, one ON/OFFperiod is calculated and the learning counter N is incremented (step122). The ON and OFF times of the switch SW are measured constantly by atimer or counter.

When the operating switch SW is turned off again less than four secondsafter the switch has been turned on the second time (NO at step 124 andYES at step 125), the program returns to step 121 again if N=2 does nothold (NO at step 126), whereupon it is determined whether the switch SWhas been turned on a third time (step 122).

When the operating switch SW is turned on the third time (YES at step122), the results of measuring the second ON and OFF times of the switchSW are accepted, learning of the second ON/OFF period is performed andthe counter N is incremented further (step 123).

When the operating switch SW is turned off again less than four secondsafter the switch has been turned on the third time (NO at step 124 andYES at step 125), the average ON/OFF period is calculated (step 127)since the value in the learning counter N is already 2 (YES at step126). That is, since the results of the second learning operation havealready been stored, the average value of the ON time and the averagevalue of the OFF time are calculated and these average values aredecided on as the ON time and OFF time in the automaticintermittent-operation mode.

Thereafter, a transition is made to the automatic intermittent-operationmode, in which the spraying operation is performed intermittently at theperiod of the previously decided ON time and OFF time as long as theswitch SW is OFF. Further, as shown in FIG. 26b, the display device LEDflashes from the moment the operating switch SW is turned off the thirdtime until the elapse of four seconds from the moment at which theoperating switch SW was turned on the third time. This presents adisplay indicating that a transition is being made to the automaticintermittent-operation mode (step 128).

The display device LED is lit during the times that the operating switchSW is ON in the first through third operations thereof and when thespraying operation is being performed in the automaticintermittent-operation mode. Further, it goes without saying that thespraying operation also is carried out during the times that theoperating switch SW is ON in the first through third operations thereof.

When the operating switch SW is subsequently turned on again for lessthan four seconds (YES at step 129, NO at step 130 and YES at step 131),the power supply is turned off (step 118).

In a case where the operating switch SW is turned off for more than fiveseconds in the course of making the transition to the automaticintermittent-operation mode (i.e., in the course of the learningoperation) (YES at step 121), this is judged as indicating an erroneousoperation or suspension of the operation; the power supply is turned offas a result (step 118).

In a case where the operating switch SW is turned on for more than fourseconds in the course of the transition to the automaticintermittent-operation mode or in the automatic intermittent-operationmode (YES at step 124 and YES at step 130), an immediate transition ismade to the continuous-operation mode (step 113).

In the embodiment described above, a learning operation is performed twotimes. However, it goes without saying that an arrangement may beadopted in which the ON time and OFF time of the operating switch SW aremeasured over a large number of times and the ON/OFF period in theautomatic intermittent-operation mode is decided based upon the results.

Further, though a forcible transition to the automaticintermittent-operation mode is made when the operating switch SW ispressed three times (in which each ON time is less than four seconds)according to the foregoing embodiment, a manual mode may be provided inwhich the user is capable of turning the operating switch on and off atall times to control the intermittency of spraying in accordance withthis ON/OFF operation. In order to distinguish between the manual modeand the automatic intermittent-operation mode, it can be so arrangedthat a transition is made to the automatic intermittent-operation modeonly after the third ON operation of the operating switch is renderedintermittent for more than four seconds. Alternatively, a special switchfor designating the automatic intermittent-operation mode can beprovided. In this case also it goes without saying that learning can beperformed one time or a plurality of times.

Industrial Applicability

An automatic atomizer is applied in ultrasonic inhalers, by way ofexample. Ultrasonic inhalers are utilized in the medical-instrumentindustry.

What is claimed is:
 1. An ultrasonic atomizer comprising: an ultrasonicpump comprising a pump shaft having an upper end, a lower end, and apump bore passing axially through said pump shaft to form openings inthe upper and lower ends, said ultrasonic pump further comprising anultrasonic vibrator mounted on said pump shaft substantially at amidpoint thereof with respect to the axial direction of said pump shaft;a liquid vessel arranged such that it is penetrated by a lower end ofsaid pump shaft; a mesh plate placed on a face of the upper end of saidpump shaft, said mesh plate having a plurality of minute holes; and aresilient biasing member for biasing said mesh plate toward the upperend face of said pump shaft, said mesh plate intermittently contactingthe upper end face of said pump shaft, wherein the upper end face ofsaid pump shaft comprises a shape in which the upper end face isslightly and smoothly curved so as to attain maximum height at theposition of the opening in the upper end of the pump bore and todiminish in height as the periphery is approached.
 2. An ultrasonicatomizer according to claim 1, further comprising: a housing configuredto support said ultrasonic pump, said liquid vessel being attached tosaid housing in a freely detachable manner; and a cap attached to aportion of said housing in a freely detachable manner so as to cover theupper end of said pump shaft; a top side of said cap being provided witha spray port, said cap having a step portion for supporting said meshplate at the periphery thereof at a position beneath said spray port,said resilient biasing member being provided between a portion of thetop side of said cap and said mesh plate.
 3. An ultrasonic atomizeraccording to claim 1, wherein said mesh plate is curved slightly by saidresilient biasing member at a peripheral edge of said mesh plateextending outwardly from the upper end face of said pump shaft, andwherein the curvature of the upper end face of said pump shaft, theelastic force of said resilient member, and the strength of said meshplate are determined such that the degree of curvature of said meshplate is less than the degree of curvature of the upper end face of saidpump shaft.
 4. An ultrasonic atomizer according to claim 1, wherein saidresilient biasing member comprises a compression coil spring.
 5. Anultrasonic atomizer according to claim 1, wherein the minute holes ofsaid mesh plate flare outwardly in a direction extending from a top sideto a bottom side of said mesh plate.
 6. An ultrasonic atomizer accordingto claim 1, wherein said mesh plate comprises a shape in which theminute holes flare outwardly in a direction extending from a top side toa bottom side of said mesh plate, and wherein a recess is formed in thetop side of said mesh plate between mutually adjacent ones of the minuteholes.
 7. An ultrasonic atomizer according to claim 1, wherein cut-outsof different size are formed in the periphery of said mesh plate atleast at two locations other than locations having point symmetry aboutthe center of said mesh plate.
 8. An ultrasonic atomizer according toclaim 1, wherein said minute holes are formed at equal intervals alongthe sides of a plurality of regular hexagons having diagonals that varyat fixed distances.
 9. An ultrasonic atomizer according to claim 1,wherein said mesh plate comprises a small area devoid of minute holessaid small area being surrounded by said minute holes.
 10. An ultrasonicatomizer according to claim 1, wherein said mesh plate comprises a smallarea devoid of minute holes, said small area opposing the opening in theupper end of the pump bore of said pump shaft over a region broader thansaid opening.
 11. An ultrasonic atomizer according to claim 1, whereinsaid mesh plate comprises an annular plate at a peripheral portion ofsaid mesh plate, wherein said annular plate causes the biasing forceproduced by said biasing member to be applied uniformly to said meshplate.
 12. An ultrasonic atomizer according to claim 1, furthercomprising a bush for encircling and supporting a portion of said pumpshaft excluding upper and lower end portions of said pump shaft, saidbush being liquid-tight; an annular lip seal, in liquid-tight contactwith a portion of the pump shaft situated higher than said ultrasonicvibrator, said annular lip seal being formed integrally at least at twolocations, one above the other, on an upper portion of said bush, and agap being provided between said portion of the pump shaft and said bushbetween the annular lip seal at the at least two locations.
 13. Anultrasonic atomizer according to claim 1, further comprising: a bush forencircling and supporting a portion of said pump shaft excluding upperand lower end portions of said pump shaft said bush being liquid tight;a housing into which said bush is fitted in a liquid tight arrangement;and a cap attached in a freely detachable manner to an annularprojecting wall that is formed on said housing about the upper endportion of said pump shaft, said cap covering the upper end portion ofsaid pump shaft when attached; a reservoir having (i) a bottom surfaceformed by a top side of said bush and (ii a peripheral wall formed by atleast one of said cap and said annular projecting wall.
 14. Anultrasonic atomizer according to claim 1, wherein a lower end of saidpump shaft is disposed in close proximity to a bottom surface or sidesurface of said liquid vessel such that residual liquid remaining insidesaid liquid vessel is pumped upon attaching to the lower end of the pumpshaft by surface tension.
 15. An ultrasonic atomizer according to claim1, wherein said liquid vessel is formed to have a recess for collectingthe residual liquid remaining inside said liquid vessel, and the lowerend of said pump shaft is disposed so as to face said recess.
 16. Anultrasonic atomizer according to claim 1, further comprising: a drivecircuit for driving the ultrasonic vibrator of said ultrasonic pump; anoperating switch; first control means responsive to an on/off operationof said operating switch for controlling the driving of said ultrasonicvibrator by said drive circuit; and second control means fordetermining, in response to said operating switch being turned on andoff at least one time, an OFF time for automatic intermittent operationbased on the ON time and the OFF time of said operating switch, and forcontrolling said drive circuit such that said ultrasonic vibrator isdriven using the ON time and the OFF time determined by said secondcontrol means.
 17. An ultrasonic atomizer in which a liquid inside aliquid vessel is supplied to an inlet side of a mesh plate formed tohave a plurality of minute holes and said mesh plate is vibrated by anultrasonic vibrator, whereby the liquid supplied to the inlet side ofthe mesh plate is sprayed from an outlet side of said mesh plate, saidmesh plate comprising a plate-shaped body having a recess betweenmutually adjacent ones of said minute holes, said plate-shaped bodybeing formed such that peripheral wall surfaces of said minute holesproject from the inlet side.
 18. An ultrasonic atomizer according toclaim 17, wherein said minute holes flare outwardly from the inlet sideto the outlet side.
 19. An ultrasonic atomizer according to claim 17,wherein cut-outs of different size are formed in the periphery of saidmesh plate at least at two locations other than locations having pointsymmetry about the center of said mesh plate.
 20. An ultrasonic atomizeraccording to claim 17, wherein said minute holes are formed in said meshplate at equal intervals along sides of a multiplicity of regularhexagons having diagonals that vary at fixed distances.
 21. Anultrasonic atomizer according to claim 17, wherein said mesh platecomprises a small area devoid of minute holes, said small area beingsurrounded by said minute holes.
 22. An ultrasonic atomizer according toclaim 17, wherein said mesh plate comprises a small area devoid ofminute holes said small area opposing a liquid-supply port over a regionbroader than said supply port.
 23. An ultrasonic atomizer comprising: anultrasonic pump comprising a pump shaft having an upper end, a lowerend, and a pump bore passing axially through said pump shaft to formopenings in the upper and lower ends, said ultrasonic pump furthercomprising an ultrasonic vibrator mounted on said pump shaftsubstantially at a midpoint thereof with respect to the axial directionof said Dump shaft; a liquid vessel arranged such that it is penetratedby a lower end of said pump shaft; a mesh plate placed on a face of theupper end of said pump shaft, said mesh plate having a plurality ofminute holes; a resilient biasing member for biasing said mesh platetoward the upper end face of said pump shaft; and an annular plateprovided on a peripheral portion of said mesh plate, or a spacerprovided between said mesh plate and the upper end face of said pumpshaft, to cause the biasing force produced by said biasing member to beapplied uniformly to said mesh plate.
 24. An ultrasonic atomizer havingan ultrasonic pump comprising a pump shaft formed to have a pump borepassing through it axially and having open upper and lower ends, and anultrasonic vibrator mounted on the pump shaft in the vicinity of themidpoint thereof with respect to the axial direction, wherein a liquidinside a liquid vessel is pumped up from the lower end of said pump boreand the liquid is supplied to a mesh plate from the upper end of saidpump bore so as to be sprayed, and wherein a bush is provided forencircling and supporting liquid tightly a portion of said pump shaft ofsaid ultrasonic pump excluding upper and lower end portions of said pumpshaft, an annular seal lip, in intimate liquid-tight contact with aportion of said pump shaft situated higher than said ultrasonicvibrator, is formed integrally at least at two locations, one above theother, on an upper portion of said bush, and a gap is provided betweensaid portion of the pump shaft and said bush between said annular seallips at the at least two locations.
 25. An ultrasonic atomizercomprising: an ultrasonic pump comprising a pump shaft having an upperend, a lower end, and a pump bore passing axially through said pumpshaft to form openings in the upper and lower ends, said ultrasonic pumpfurther comprising an ultrasonic vibrator mounted on said pump shaftsubstantially at a midpoint thereof with respect to the axial directionof said pump shaft; a liquid vessel arranged such that it is penetratedby a lower end of said pump shaft; a mesh plate placed on a face of theupper end of said pump shaft, said mesh plate having a plurality ofminute holes; a resilient biasing member for biasing said mesh platetoward the upper end face of said pump shaft; a bush for encircling andsupporting liquid tightly a portion of said pump shaft of saidultrasonic pump excluding upper and lower end portions of said pumpshaft; a housing in which said bush is fitted liquid tightly; and a capattached in a freely detachable manner to an annular projecting wallthat is formed on said housing about the upper end portion of said pumpshaft, said cap for covering the upper end portion of said pump shaft; areservoir having a top side of said bush forming a bottom surface and atleast one of said cap and said annular projecting wall forming aperipheral wall.
 26. An ultrasonic atomizer according to claim 25,wherein a top side of said cap is provided with a spray port, a stepportion is formed for supporting said mesh plate at the peripherythereof at a position beneath said spray port, and said resilientbiasing member is provided between a portion of the top side of said capand said mesh plate.
 27. An ultrasonic atomizer having: a liquid vesselfor accommodating a liquid to be atomized; and an ultrasonic pumpcomprising a pump shaft having a lower end situated inside said liquidvessel and formed to have a pump bore passing through the pump shaftaxially and having open upper and lower ends, and an ultrasonic vibratormounted on the pump shaft, wherein a bottom surface or a surface of saidliquid vessel is formed to be oblique with respect to a horizontalplane: a lower end of said pump shaft being disposed in close proximityto the oblique bottom surface or the oblique side surface of said liquidvessel such that residual liquid remaining inside said liquid vessel ispumped upon attaching itself to the lower end of the pump shaft bysurface tension and ultrasonic vibration.
 28. An ultrasonic atomizeraccording to claim 27, wherein said liquid vessel comprises a recess forcollecting the residual liquid remaining inside said liquid vessel, andwherein the lower end of said pump shaft is disposed so as to face saidrecess.
 29. An ultrasonic atomizer according to claim 27, wherein saidliquid vessel is freely attachable and detachable.
 30. An ultrasonicinhaler having an ultrasonic pump comprising a pump shaft formed to havea pump bore passing axially therethrough, said pump further comprisingan ultrasonic vibrator mounted on said pump shaft, wherein liquid ispumped through said pump shaft and sprayed by ultrasonic vibration, saidinhaler comprising: a drive circuit for driving the ultrasonic vibratorof said ultrasonic pump; an operating switch; first control meansresponsive to on/off operation of said operating switch to control thedriving of said ultrasonic vibrator by said drive circuit; and secondcontrol means for determining, in response to said operating switchbeing turned on an off at least one time, an ON time and an OFF time forautomatic intermittent operation based on the ON time and the OFF timeof said operating switch, and for controlling said drive circuit in suchthat said ultrasonic vibrator is driven using the ON time and the OFFtime determined by said second control means third control means forcontrolling said drive circuit to drive said ultrasonic vibratorcontinuously in response to an ON time of said operating switch that isgreater than a first predetermined time.
 31. An ultrasonic inhaleraccording to claim 30, wherein said second control means performsautomatic intermittent operation in response to on/off operation of saidoperating switch being repeated a prescribed number of times.
 32. Anultrasonic inhaler according to claim 31, wherein said second controlmeans transitions to automatic intermittent operation upon verifyingthat the ON time of said operating switch for the last time in theprescribed number of times is greater than a second predetermined time.33. An ultrasonic atomizer according to claim 30, further comprising anautomatic intermittent-operation mode switch, said second control meansinitiating automatic intermittent operation in response to an input fromsaid automatic intermittent-operation mode switch.
 34. A method ofcontrolling an ultrasonic inhaler having an ultrasonic pump comprising apump shaft formed to have a pump bore passing axially therethrough, andan ultrasonic vibrator mounted on said pump shaft, wherein liquid ispumped through said pump shaft and sprayed by ultrasonic vibration, saidmethod comprising: driving said ultrasonic vibrator during a time inwhich an operating switch is ON; measuring a duration of the ON time;halting driving of said ultrasonic vibrator during a time in which theoperating switch is OFF; measuring the duration of the OFF time;determining an ON time and an OFF time for automatic intermittentoperation based on the measured ON time and OFF time of said operatingswitch after said operating switch has been turned on and off and aprescribed number of times; said ultrasonic vibrator intermittentlyusing the determined ON and OFF times when an ON time of said operatingswitch is less than a predetermined time; and driving said ultrasonicvibrator continuously when the ON time of said operating switch isgreater than or equal to the predetermined time.